Parallel adder using majority decision elements



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Jan. 17, 1967 M. COHEN 3,299,260

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Jan. 17, 1967 M. COHEN 3,299,260

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Propag a fion c/rcu/f /cPcf A /n venian Marr/s Gabe BJ/f mv J MMV@ United States Patent C) 3,299,260 PARALLEL ADDIER USING MAJORITY DECRSIN ELEMENTS Morris Cohen, Los Angeles, Calif., assignor to The National Cash Register Company, Dayton, hio, a corporation of Maryland Filed Aug. 6, 1953, Ser. No. 300,202 18 Claims. (Cl. 23S- 173) The present invention is directed to computer circuits for performing logical operations and, more particularly, to electronic digital circuitry for performing logical operations for processing data.

According to the preferred embodiment of the present invention, networks of majority decision elements or devi-ces are provided for performing the function of adding numbers 'which are expressed in binary-coded decimal form, i.e., each decimal digit is represented by a combination of binary digits l and 0. Each of the majority decision elements is provided with a plurality of inputs and is capable of assuming either a binary l or a binary operating output state according to whichever one of the binary signals 1 or 0 is predominant at the inputs thereof. In the preferred arrangement of the present invention, the majority decision elements comprise magnetic thin lm parametric elements of the type disclosed in detail in a copending application of Bruce A. Kaufman entitled Parametrical Device, and Apparatus, Ser. No. 43,801, led on July 19, 1960, and an article entitled On the Characteristics of Cylindrical Thin Film Parametrons Pumped to Saturation, published in the May 1963 Proceedings of the IEEE. It has been found that the reliability of each of these thin film parametric elements is such as to be capable of accepting as many as seven binary signal inputs and of assuming either one of the operating binary states 0 4or 1" to produce an outp-ut corresponding to the majority of these binary inputs.

The majority decision principle which is employed to the best advantage in the present invention enables a single seven input majority decision computer element to represent a fairly complex function (majority decision function) such that a network of these elements for performing a given logical operation, e.g., addition, can be realized with less components and less logical levels than networks employing majority decision elements limited to a fewer number of inputs or networks employing other more conventional components such as diodes and transisters. Thus, although the time required for operation of networks formed of known majority decision elements is generally of longer duration than the operation of networks formed of other more conventionall components, such as high speed transistor and diode logical circuits, the realization of more complex functions by a single majority decision element is important in providing overall higher speed of operation of adder circuitry and other similar electronic digital logical devices.

Briey, the present invention, as disclosed hereinafter by a preferred embodiment thereof, is directed to an adder for operating in a parallel fashion on a pair of numbers expressed by binary-coded decimal digits to produce the sum thereof. This adder comprises a plurality of adder stages (the prefered embodiment has twelve stages) wherein an adder stage is provided for each order of numerical value of the decimal numbers whose sum is desired. Each adder stage comprises a decimal unit for performing partial binary addition, a carry digit propagation circuit and a carry digit incorporation circuit. The combination of adder stages provides for parallel summing of the multiple digit numbers applied to the inputs of the adder. Each of the partial binary adder units comprises four parallel binary adder circuits (one for each of the four binary bit positions 20, 21, 2Z and 23) for directly producing binarycoded decimal partial sum signals for each of the corresponding pairs of binary-coded decimal digits of the numbers applied to the inputs thereof and a carry detector circuit for producing carry digit signals. These carry digit signals are applied to the carry propagation circuits to provide for propagation of the carry digit signals from lower order decimal adder stages to higher order adder stages in order to distribute carry digit signals to the higher ord-er stages of the carry incorporation circuits to enable the sum to be formed at the adder output in a minimum time interval.

One of the novel features of the partial adder circuits of the present invention is the provision of binary-coded decimal out-put signals in each adder stage representing the partial sum (mod 10) of a pair of decimal digits of the same order, without the need of decimal correction, even when the partial sum is ten (10) or more. The term partial sum (mod 10), as used herein, designates a sum that does not take into account carry digits and thus does not exceed nine (i.e., 0 to 9, inch); and (mod l0) is the commonly known abbreviation of modulo 10.

Another feature of the present invention, which enables a reduction in the number of logical levels to obtain a final sum, is provided by the carry digit detector circuit. The carry detector circuit for each adder stage detects a partial sum equal to or greater than nine (9) to produce a carry propagation signal, and also detect-s a partial sum equal to or greater than ten (10) to produce la true carry digit signal which is referred to hereinafter as a carry digit originating signal. Both the carry digit propagation signa-l and the carry digit originating signal are initiated immediately, prior to the complete production of the partial sum (mod 10) signals, to enable the carry digit signals to more rapidly reach each of the decimal stages and to be accounted for, in forming the nal sum, thereby decreasing the number of levels of logic and the time required to obtain the sum of the numbers being added. A carry digit originating signal will always generate an interstage carry digit signal (K) for the next higher order adder stage of the carry incorporation circuits. A carry digit propagation signal will only generate an interstage carry digit signal (K) for the next higher order stage of the carry digit incorporation circuit when the next lower adder stage generates an interstage carry digit signal K. The carry digit signals generated in the carry digit propagation circuit are combined with the partial sum (mod 10) signa-ls to provide the true sum, including the carry digits, in a manner to be disclosed more fully hereinafter in the detailed description of the present invention.

Accordingly, it is an object of the present invention to provide a novel, fast acting, parallel operated digital adder having the foregoing features and advantages.

Another object of the present invention is the provision of an adder for summing binary-coded decimal digits in parallel in which the logical functions are performed by majority decision elements.

A further object of the present invention is to provide' for the addition of digits in which the logical functions 'involved in the addition are performed by magnetic thin Si which produces the complete sum of two twelve decimal digit numbers during an overall operating period involving six logical levels.

Another object of the present invention is to provide a novel arrangement of majority decision elements for propagation and generation of carry digit signals.

A still further object of the present invention is the provision of carry digit propagation circuits that utilize redundant carry information to simplify the circuitry involved and minimize the number of logical levels required to propagate carry digit signals from lower order adder stages to higher order adder stages.

Other objects and features of the invention will become apparent to those skilled in the art as the disclosure is made in the following detailed description of a preferred embodiment of the invention as illustrated in the accompanying sheets of drawings in which:

FIG. 1 is a block diagram showing a parallel, binarycoded decimal adder and also a timing clock source for supplying timing signals thereto, for illustrating the general arrangement of the preferred embodiment of the adder of the present invention;

FIG. 2a is a more detailed block diagram of three adder stages of the adder shown in FIG. l, for illustrating the operation of adding typical binary-coded decimal digits of the augend and addend in parallel fashion;

FIG. 2b is a diagram showing the timing signals for controlling the operation of the parallel, binary-coded decimal digit adder shown in FIGS. l and 2a;

FIG. 2c illustrates an example of the operation of addition as performed on binary-coded decimal digits by the three adder stages of the parallel, decimal adder shown in FIG. 2a;

FIG. 3 is a block diagram of adder stage #l of the adder shown in FIGS. l and 2a and is typical of the adder stages of the adder of the preferred embodiment;

FIG. 4a shows the binary system of representing decimal digits of the adder inputs in Table l and partial sums (mod l) in the same binary system in Table 2;

FIG. 4b shows Table 3 which sets forth the binary l states only of majority decision elements of the partial adder circuit (20) in response to combinations of the lowest order binary-coded decimal digit signals of the augend andaddend;

FIGS. 4c, 4d and 4e show Tables 4, 5, and 6, respectively, which set forth the binary l states only of majority elements of the respective partial adder circuits (21, 22 and 23) in response to typical binary-coded decimal digit signals representing partial sums requiring binary 1" signals on the outputs of the respective circuits;

FIG. 5a is a schematic illustratio-n of a typical majority decision element wherein the majority decision functions performed by this element are illustrated by Boolean equations;

FIGS. 5b and 5c are equivalent schematic diagrams of the same typical portion of the network of majority decision elements of the partial adder circuits (21) `shown in FIG. 7, and are shown here only for the purpose of clarication of the diagrammatic illustrations of the networks of majority decision elements in the remainder of the drawings showing the adder of the present invention;

FIG. 6 is a schematic diagram of the partial adder cir* cuit of the adder stage #1, shown in block diagram in FIG. 3, which is operative to provide a binary-coded decimal partial sum (mod l0) of the least significant digits of the augend and addend, and this circuit is typical of partial adder circuits (20) of the other adder stages of the adder of the preferred embodiment of the invention;

FIGS. 7, 8 and 9 are schematic diagrams of the other partial adder circuits (21, 22 and 23), respectively, of adder stage #1, shown in block diagram in FIG. 3, and these circuits are typical of respective partial adder circuits (21, 22 and 23) of the other adder stages of the adder of the preferred embodiment of the invention;

FIG. l0 is a schematic diagram of the carry detector circ-uit of adder stage #1, shown in block diagram in FIG. 3, for producing carry signals indicating a partial sum of the least signicant digits as equal to or greater than ten (10) and/or equal to or greater than nine (Q) and this circuit is typical of the carry detector circuits of the adder stages of the adder of the preferred embodiment of the invention;

FIGS. 11a and 1lb comprise a `schematic diagram of all the carry propagation circuits for all twelve adder stages (#1 to #12, incl.), which circuits provide for propagating carry digit signals from lower order adder stages to higher order adder stages of the twelve stage adder illustrated by the block diagram in FIG. 1;

FIG. 12 is a schematic diagram of the carry incorporation circuit for the adder stage #l which provides for combining the partial sum (mod l0) and carry digit signals to produce the sum for adder stage #1; and this circuit, as shown, is typical of the carry incorporation circuits of the lower order adder stages providing for a single carry digit signal input;

FIG. 13a is a schematic diagram of the carry incorporation circuit for adder stage #lo and this circuit is typical of corresponding carry incorporation circuits for the higher adder stages providing for three carry digit signals;

FIGS. 13b and 13C show the input lines and terminals only for carry incorporation circuits for adder stages #1I and #I2 providing for three carry signals;

FIG. 14 is a schematic diagram of a serial, decimal adder circuit ('20) of the rst alternate embodiment of the present invention which has provision for a carry signals input to provide for serial operation in the addition of numbers;

FIG. 15a is a schematic diagram showing the binary partial adder circuits and binary carry incorporation circuits of adder stage #I of the second alternate embodiment of the binary parallel adder of the present invention which provides for addition of numbers represented in pure binary notation;

FIG. 15b is a schematic diagram showing the binary carry detector circuit of adder stage #l of the second alternate embodiment of FIG. 15a; and

FIG. 15C is a schematic diagram of carry incorporation circuit for adder stage #I0 of the second alternate embodiment which provides for incorporation of three binary carry digit signals.

GENERAL DESCRIPTION (FIG. l)

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, FIG. 1 shows the parallel, majority logic adder 20 which compromises the preferred embodiment of the present invention. The adder 2t) accepts binary-coded decimal digit signals at its augend and addend inputs, and operates to produce a sum expressed by binary-Coded decimal digit signals at its sum output. The binary-coded decimal digit signals representing the augend and addend are applied to inputs of the adder 2i) simultaneously, i.e., in parallel, and the decimal units 22 operate to produce partial sums (mod 10) and carry signals. Carry propagation circuits 24 have carry digit signal inputs coupled to the decimal units 22 and provide for propagation of the carry signals from the lower order to higher order adder stages of carry incorporation circuits 26 where the partial sum outputs of the decimal units 22 are modied to include the carry signals to produce the sum at the sum output.

The adder 20 shown in FIG. 1 comprises networks of majority decision elements and preferably of parametric elements, such as P10, P100, P and Plb, for example as shown in FIGS. 5b and 5c, which elements are supplied high frequency timing signals designated subcl-ocks I, II and III from a clock source 28 for timing their operation. The subclocks I, II and III are generated by the clock source 28 to provide for synchronous operation of the adder 20 at a desired clock repetition rate, eg., 200 kilocycles. At this clock rate, an operating cycle of the majority decision elements in adder 20 has a time period of 5 microseconds, as illustrated by the timing diagram of FIG. 2b. The clock source 28 may comprise, for example, a sinusoidal signal wave generator producing a 20 megacycle signal (2f) which is modulated at the clock rate to produce overlapping subclock signals, I, II and III in any known manner, eg., as disclosed in the previously cited copending application. As shown by the timing diagram of FIG, 2b, an addition time period, l0 to I6, which is the period of time required to provide the sum of the augend and the addend, includes two successive operating cycles No. 1 and No. 2 of overlapping subclock signals I, II and III. Since cycles No. 1 and No. 2 are identical repetitive cycles, a new augend and a new addend can be applied to the adder every subclock I time so that operations involving two independent setsof augend and addend can be performed in the adder 20 at the same time. However, to simplify the description which follows, the operation herein is described in connection with the addition of the exemplary augend (367) and addend (435) applied to the adder inputs as shown in FIG. 2a. Accordingly, decimal units 22 (FIG. 1) are described as being operative in the first operating cycle No. 1, including subclocks I, II and III, to produce the partial sums (mod and carry signals, and the carry incorporationcircuits 26 are described as being operative in the second operating cycle No. 2 to produce the sum at the sum output at the end of the addition time period. Carry propagation circuits are operative during subclock III of operating cycle No. 1 and subclock I of operating cycle No. 2. During the time interval of these latter subclocks III and I, sufcient time is provided to propagate the carry signals from the lower order adder stages to the higher order adder stages.

In the drawings and detailed description of the present invention, certain letters and numbers have been grouped to provide reference characters which designate particular circuits, inputs, outputs or parts of the adder 20. In accordance therewith, small letters a, b, and c, have been included in reference characters designating the augend binary digit inputs of respective adder stages #1, #2 and #3; and corresponding small letters a, b and c have been included in reference characters designating partial sum (mod 10) signal outputs, carry digit signal outputs and sum outputs of respective adder stages #1, #2 and #3. For example, in FIG. 2a, reference characters for adder stage #1 include reference characters a1, a2, a4 and a8 to refer to respective ones of four inputs for a set of four binary-coded decimal digit signals representing the least significant decimal digit of the augend; reference characters R9a and R10a to refer to carry digit signal outputs; reference characters Spila, SpZa, Sp4a and SpSa to refer to respective ones of four partial sum (mod 10) outputs; and reference characters Sla, S2a, S4a and SSa to refer to respective ones of four sum outputs. A partial sum (mod 10) is referred to by the letters Sp which are followed by a digit designating the stage, eg., Sp1 is the partial sum (mod 10) of stage #1. Similarly, carry signal outputs K1, K2 and K3 of the carry propagation circuits are provided for interstage carry signals applied to carry incorporation circuits for adder stages #1, #2 and #3, respectively. As to reference characters for adderinputs for binary-coded decimal signals representing the addend, small letters d, e, and f have been employed, as shown in FIG. 2a, to refer to adder inputs for adder stages #1, #2 and #3, respectively.

DETAILED DESCRIPTION (FIG. 2a)

In FIG. 2a, adder stages #1 to #3 only are shown in the `block diagram to provide a basis for a detailed description of the operation of system of the adder 20. The description of decimal adder stages #1 to #3 is typical of the operation of the various adder stages and the description of stages #l to #3 will provide a complete understanding of the system operation of the adder 20. Each of the adder stages #1 to #12, for example, includes a decimal unit 22 and a carry incorporation circuit 26. Thus, adder stage #l includes a decimal unit #1, a carry incorporation circuit (CIC #1), and a carry propagation circuit (CPC #1), which latter circuit is shown included with the other carry propagation circuits 24 (CPC `#1- #3) in the lower part of the drawing. The adder stage #1 accepts ybinary-coded decimal signals representative of the lowest order decimal digits of the augend and addend, e.g., "7 and 5, to provide the lowest order decimal digit of the sum S1 thereof, eg., 2, at its sum outputs Sla, SZa, S411 and 58a.

As shown in FIG. 2a, inputs to the decimal adder stage #1 include inputs a1, a2, a4 and a8 on which a set of four binary-coded decimal digit signals are applied representing the least significant decimal digit 7 of the augend; and inputs d1, d2., d4 and d8, on which a set of four binary-coded decimal signals are ap-plied representing the least significant decimal digit 5 of the addend. The binary representation of decimal digits, such as provided by signals on inputs a1, a2, a4 and a8 is shown in the Table 1 of FIG. 4a. The binary signals which are representative of the binary states 0 and l comprise high frequency signals having a common parametric oscillation frequency (f) which is of the phases zero and pi radians, respectively. For example, when a majority decision element is oscillating at a high frequency having a phase of zero radian, the element is in the binary 0 state; and when a majority decision element is in oscillation in the phase of -pi radians, the element is in the binary 1 state. The inputs a1, a2, a4, a8 and d1, d2, d4, d8 of decimal unit #1, as shown, comprise high frequency signals (f) having a phase of zero and pi radians, and a signal of a phase of zero radian is indicated by the ybinary digit 0 and a signal of pi radians is indicated by a binary digit 1.

To illustrate the operation of the adder 20, FIG. 2a shows the decimal unit #1 to have binary-coded decimal digit input signals 0111 for the decimal digit 7 and binary-coded decimal digit signals 0101 for the decimal digit 5. The partial sum (mod 10) Sp1 of these input signals is 0010 which is produced during subclock III, of operating cycle No. 1 at outputs Spla, SpZa, Sp4a and SpSa. Also, binary signals l are produced during subclock II of operating cycle No. 1 at carry detector signal outputs R901 (9) and RlOa (10) of the decimal unit #1 to be utilized in carry propagation in a manner to be described in detail later. The partial sums (mod l0) are produced in binary-coded decimal digit form directly without the need of modification or conversion as required in many prior systems. The partial sum (rnod 10) Sp1 of decimal unit #1 need not be modiiied or converted therefore, to binary-coded decimal digit form and the only operation that remains is to incorporate a carry input, if any, lat the carry incorporation circuit (CIC #1) to provide the sum S1.

Decimal units #2 and #3 are arranged in parallel with decimal unit #1 and operate `concurrently on the respective binary input signals for the remaining digits of the augend and addend to produce partial sums (mod 10) Sp2 and Sp3 for decimal adder stages #2 and #3, respectively. Decimal unit #2 responds to binary-coded decimal digit signals 0110 applied to inputs b1, b2, b4, [28 and signals 0011 applied to inputs e1, e2, e4, e8 to add the next higher order decimal digits 6 and 3 of the augend and addend to provide the partial sum (mod 10) Sp2. Decimal unit #3 responds to binary-coded decimal digit `signals 0011 applied to inputs c1, c2, c4, C8 and signals 0100 applied to inputs f1, f2, f4, f8 to produ-ce the partial sum (mod 10) Sp3 of the next higher order decimal digits 3 and 4 of the augend and addend, respectively. The carry signal outputs RQa-Rla, R9b-R10b and R9c-R10c of decimal units #1 to #3 are coupled to the carry propagation circuits 24 to provide for the propagation of the carry signals from the lower order stages to the higher `order stages. As indicated, the carry outputs R9c and R10c are also coupled to carry propagation circuit (CPC #5) to provide for propagation of the carry to higher order decimal adder stages.

Referring now more particularly to the carry propagation functions of the adder 20, as shown in FIG. 2a, the carry propagation circuits 24 (CPC#1-#3) are operative during subclock III of cycle No. 1 and subclock I of cycle No. 2. Accordingly, the carry signals provided by the decima-l units #1 to #3 at the outputs R9a- Ra, RWI-R101) and R9c-R10c are produced prior to associated partial sums (mod 10) Sp1, Sp2 and Sp3. The timing of Operation of partial addition and carry detection in the decimal units #1-#3, carry propagation in circuits (CPC #3) and carry incorporation in circuits (CIC #Ir-#3) is indicated in the timing diagram FIG. 2b. The decimal units #1 to #3 include the operation of partial addition in operating cycle No. 1 during the time interval t0 to t3. The other operation of the decimal units #1 to #3 is the carry detection function in which a partial sum equal to or greater than nine (9) and/or equal to or greater than ten (10) is detected in the time interval l0 to t2 to produce binary 1 carry signals at the respective outputs R9a and R10a. The carry propagation circuits (CPC #1-#3) are operative in the time interval t2 to t4. These circuits begin their operation during subclock III of operating cycle No. 1 and continue over through subclock I of operating cycle No. 2. Thus, lthe carry signals at the outputs K1 to K3 of the carry propagation circuit 24 (FIG. 2a) are made available and applied to the carry incorporation circuits (CIC #ll-#3), respectively, at time t4 during subclock II `or" operating cycle No. 2. The carry signals K1, K2 `and K3 are applied to the carry incorporation circuits (CIC #1r-#3), as shown, to be combined with the respective partial sums (mod l0) Sp1, Sp2 and SP3 to produce the sums S1 to S3 at the outputs of the carry incorporation circuits (CIC #1-#3) at the end of operating cycle #2 (time t6). The carry signal K4 is utilized in the higher adder stage #4 in carry incorporation circuit (CIC #4), not shown in FIG. 2a.

The operations of the adder in providing the surn of the augend 367 and addend 435 are indicated as shown in the example in FIG. 2c. In the first column under the column heading Decimal the augend 367 and addend 435 are shown in decimal form. The binary-coded decimal form is shown in subsequent columns under the corresponding adder stage numbers #3, #2 and #1. The small letters in parenthesis (a) (b) (c) (d) (e) or (f), as shown, following respective groups of binary-coded decimal digits, e.g., 0111 (a), correspond to the respective letters designating the inputs of decimal units #1 to #3 The partial sums (mod 10) Sp of the corresponding digits of the augend 367 and addend 435 are shown in decimal form 792 and in binary-coded decimal form 0111 (SP3), 1001 (Sp2) and 0010 (Sp1). The `operation of partial addition is provided by partial adder circuits 30, 32, 34 and 36 (FIG. 3) of decimal units #1 to #3 to produce the partial sums (mod l0) which do not include the carry. Carry signals at outputs R9a-R10a, RNs-R10!) and R94:- R10c are produced by carry detector circuits in the decimal units #1 to #3, e.g., carry detector circuit 33 (FIG. 3), and as indicated in the columns #3, #2 and #1 under the heading Carry Propagation (FIG. 2c). The carry sinnals K1, K2 and K3 are combined with the par- :iia-l sums (mod 10) Sp1, Sp2 and S113, respectively, in the carry incorporation circuits (CIC #1-#3) to produce binary-coded decimal digit sums 0010 (S1), 0000 (S2), and 1000 (S3) which correspond to the decimal sum 802 (S).

The addition of ythe augend 367 and the addend 435 to obtain the partial sum (mod 10) is clearly indicated in FIG. 2c. For example, the sum of decimal digits 7 and 5 equals 12 and the partial sum (mod 10) equals 2 with a decimal carry. In decimal unit #1 of adder stage #1, the addition of binary-coded decimal digits (equivalents of decimal digits 7 and 5) 0111 (a) and 0101 (d) produces a partial sum (mod 10) 0010 (Sp1) which is the binary-coded decimal digit equivalent of the decimal digit 2. The carry signal K2, obtained during this partial addition, is indicated in the column #1 (FIG. 2c) of Carry Propagation (for adder stage #1). The carry signal K2 is produced as a result of the partial sum being equal to or greater than nine (9) and equal to or greater than ten (10) as shown by the binary carry signals 1 and l next to outputs (R951) and (R10a). This carry signal K2 is applied to the carry incorporation circuit (CIC #2), FIG. 2a, to be combined with the partial sum output 1001 (Sp2) of adder stage #2 (FIG. 2c). Thus, the partial sum 1001 (Sp2), or decimal digit 9, is added to the carry (1) (K2) to produce the sum 0000 (S2), or decimal digit 0. It should be noted that while in the foregoing discussion, the carry signal (1) (K2) is produced in carry propagation as a result of a 1 bit at the output R10a, the carry signal (l) (K3) is produced in carry propagation as a result of a 1 bit at each of the outputs R9b and R10a even though a 0 bit is present at output R10b. This demonstrates, in part, the reason for producing outputs R9a, R9b and R9c, i.e., to produce carry signals in any adder stage after the partial sum is found to be equal to 9 in the presence of a carry signal K from a lower order stage. The carry signal (1) (K3) is added to the partial sum (mod 10) 0111 (SP3) of adder stage #3 to produce the sum 1000 (S3) for adder stage #3, or the decimal digit 8. Thus, the combined sum of the outputs of stages #1 to #3 is the decimal sum 802. In View of the foregoing discussion of FIG. 2c, certain operations of addition performed by each of the stages of adder 20 should now be readily apparent.

DETAILED DESCRIPTION oF ADDER STAGE #i (Ero. 3)

Referring to FIG. 3,`the details of the decimal adder stage #1 are shown to include the decimal unit #1 which includes partial adder circuits 30, 32, 34, 36 and the carry detector 38. As stated before in the description .of FIG. 2a, the adder stage #1 also includes the carry propagation circuit (CPC #1) and the carry incorporation circuit (CIC #1). The adder stage #1, as shown, is a typical adder stage of the adder 20. The partial sum (mod 10) (Sp1=0010) is the partial sum of the least signicant digits 7 and 5 of the augend 367 and addend 435 and is produced in adder stage #1 by the partial adder circuits 30, 32, 34, and 36. The rst of these partial adder circuits, circuit 30, is shown to have only a single pair of inputs a1 and d1, and each of the remaining partial adder circuits for adder stage #1 has an input for each of the eight bits representing decimal digits 7 and 5. The carry detector circuit 38 is also provided with an input for each of the eight bits representing the decimal digits 7 and 5.

The partial sum outputs Spla, Sp2a, Sp4a and Sptia (FIG. 3) of the partial adder circuits 30, 32, 34 and 36, respectively, are coupled directly to the carry incorporation circuit (CIC #1) to be incorporated with the carry output K1 from the carry propagation circuit (CPC #1) during subclock II of cycle No. 2. The combination of carry output K1 and the partial sum outputs Sp1a, Sp2a, Sp4a, and SpSa in the carry incorporation circuit (CIC #1) produces the `sum S1 for stage #1. Carry detector circuit 38 is responsive to the binary signal inputs for the decimal digits 7 and 5 to produce carry signals indicating whether a partial sum for stage #1 will be equal to or greater than nine 2 9) and/or equal to or greater than ten (10) by outputs R9a and R10a, respectively. The outputs R9a and R10a are coupled to carry propagation circuit (CPC #1) along with carry input signal Kin. It should be noted that adder stage #1 actually does not ordinarily have a carry input signal Kin, since it is the first stage of the adder. However, to show adder stage #1 as a typical stage, the carry input is shown with the signal Kin as a binary O signal. Since the sum of exemplary decimal digits 7 and 5 is both equal to or greater than nine (9) and equal to or greater than ten (10), the output R9cz is binary 1 and the output R10a is binary 1. Also, since carry input -signal Kin is binary for the first stage, no carry digit into the adder stage #1 is present and hence output R9a is of use only when the partial sum in stage #1 is equal to or greater than ten (10). When the partial sum is equal to or greater than ten (10), both outputs R9a and R10a are binary l outputsand both of the l outputs are used in the carry propagation circuit (CPC #1) to produce an interstage carry signal K1. A more complete understanding of the operation of the carry propagation circuit (CPC #1) and use of outputs R9a and R10a therein will be provided by the detailed description of FIGS. lla and 1lb. While adder stage #1, as shown, is considered to be typical of the other adder stages, it is to be noted that the details of the carry propagation circuits 24 for the different adder stages are not identical. Therefore, carry propagation circuits are shown for each of the adder stages in FIGS. 11a and 11b. Before entering into a discussion of the details of operation of the various adder circuits shown in FIGS. 6 to 13, their diagrammatic representations will next be discussed in connecton with FIGS.va, 5b and 5c.

DESCRIPTION OF DIAGRAMMATIC REPRESEN- TATIONS OF CIRCUITS (FIGS. 5a, 5b AND 5c) Certain circuit conventions have been employed which use symbols, notations and abbreviations in descriptions of parametric majority decision elements. Since the majority decision elements of the preferred embodiment of the present invention employ parametric elements, the schematic diagrams of the networks of majority decision elements have been shown in a simplified form to aid in the understanding of the operation. In FIG. 5a, a typical majority decision element Px, as used in the present embodiment, is shown to comprise a parametric element having control inputs A, B, C, D and E and a binary l constant control input indicated by the l in the circle (which circle is the symbol for the parametric element Px). The parametric element Px has control inputs which have equivalent value or weighted value of seven single control inputs, a double control input A (value=2); single inputs B, C, D and E; and a single constant binary l input (indicated by the l in the circle).

The complex function provided by the majority decision element Px (FIG. 5a) is shown by either one of the Boolean equations (shown in maximum form or reduced form) in order to provide some indication of the power and advantages of majority decision elements in a network for performing various logical functions such as those involved in the parallel addition of plural digit numbers. The realization of complex functions by a single majority decision element such as element Px, has been found to be effective in reducing the number of logical levels in performing such functions as addition.

In FIG. 5b, only a portion of the partial adder circuit 32, shown in block diagram in FIG. 3 and in FIG. 7, has been shown for the sole purpose of illustrating the schematic diagram representations employed in the remainder of the drawings which show the details of the circuitry for the partial adder circuits land other circuits of the adder 20. In FIG. 5c, the circuit details shown in FIG. 5b are illustrated schematically to provide easy reference to the symbols, notations and representations used herein. Majority decision elements P10, Pa, P10b l0 and P13a, as shown, comprise parametric elements of the type disclosed in the cited copending application. i The majority decision element P10, for example, comprises a thin film magnetic rod 40 consisting of a copper-beryllium conductor substrate having a cylindrical, axially oriented, anisotropic thin film of nickel-iron alloy deposited thereon, e.g., by electro-deposition. The term thin film is used herein in its technical sense, i.e., the thin iilrn exhibits single magnetic domain characteristics. As shown in FIG. 5b, subclock I is coupled to the conductor substrate to provide an exciting current in rod 40 which is inductively coupled to a winding 42. The tuned circuit including a capacitor 43a, oscillates at a frequency (f) which is one-half the frequency (2f) of the subclock I. The phase of the oscillations of the tuned circuit is controlled by the phase of the binary control signals (zero or pi radians) applied to the control inputs a1, d1, a2 and d2 and the phase of the constant signal (zero radian) applied to control input Pk (0). All of these inputs are coupled to the tuned circuit by a toroidal core 44 functioning as a transformer, as shown in FIG. 5b. The phase of the resulting parametric oscillations produced by theelement P10 is either Zero or pi radians, corresponding to the binary stages 0 or 1, respectively. Accordingly, a majority value of control signal inputs of zero phase will cause the majority decision element P10 to produce parametric -oscillations at the frequency (f) of the zero phase to provide an output signal having a frequency (f) of the zero phase corresponding to the binary state 0. However, it is important to note that a control input of the various majority elements can have a single value, double value, triple value (or more) in determining the majority value of the binary l or 0 signals applied to the control inputs and it is the resultant of these differently weighted control inputs which determines a net signal of binary 0 or 1 that controls the phase of parametric oscillations of any one of majority decision elements being considered. Thus, in FIG. 5b, the majority decision element P10, for example, has a control input a2, which has a double value (value=2) because the winding has two turns on the toroidal core 44. The effect of the two turns is to produce a control signal having twice the amplitude of a single value control input, such as control input a1, which has but a single turn. An example of a triple value input is illustrated by the constant control input Pk (l) of the majority decision element P10b. It should be further noted that the direction of the winding on the core 44 is important, Thus, if the direction of the winding is reversed, the elfect is to induce a signal of the opposite phase at the respective control input.

As noted before, the exemplary binary signals as shown in FIG. 5b, applied to control inputs for the majority decision element P10, place it in the binary 0 state. The control inputs a2 and d2 each have a double value and each of the control inputs a1 and d1 and constant control input Pk have only a single value. However, a close Aexamination of the control inputs to majority element P10 shows that the winding of input a2 is reversed relative to the other windings, to invert the phase of the binary l signal (pi phase) applied thereto to produce a double value binary 0 control signal (zero phase). In view thereof, the majority value of the control inputs to element P10 including the binary 0 constant control input Pk (0) results in a binary 0 net signal having a phase of zero radian. Accordingly, the majority element P10 is caused to oscillate in the zero phase, which corresponds to the phase of zero radian of vthe net signal, to place the element P10 in the binary 0 state to produce a binary 0 signal (zero phase) at its output.

The binary O signal (zero phase) on the output of the majority decision element P10 is coupled to control inputs of majority decision element P10a and majority decision element P13a along with other binary signals applied to control inputs as shown in FIG. 5b. The binary signals applied to the control inputs, including the constant control input to the majority decision element P1011, have a majority value in the phase of zero radian, therefore, the majority decision element P10a is caused to oscillate in the phase of zero radian to produce the binary O signal at its output. The majority decision element P13a is placed in the binary l state by control signals having a majority value of a phase of pi radians to produce a binary 1 signal at its output. The binary and l signals on the outputs of majority decision elements P10a and P13a are coupled to control inputs of the last majority decision element P1011, along with other control inputs, as shown in FIG. b, to produce a binary l net signal to cause the majority decision element P101: to be placed in a binary l state (phase of pi radians) to produce a binary l signal (pi radians) at its output Sp2a.

In FIG. 5c, the identical circuit shown in FIG. 5b has been shown simplied using the schematic illustrations employed hereinafter to describe the various circuit arrangements of the adder 20 of the present invention.

Corresponding reference numbers refer to corresponding parts in FIGS. 5b and 5c. In FIG. 5c, double Value inputs (two turn windings), e.g., a2 and d2 are indicated by a single line having two branches leading into the majority decision element P (circle); and single value inputs (one turn windings), eg., a1 and d1, each has only a single line leading into the majority decision element P10. The binary 0 constant control input Pk (O) is a single value input which is designated by the 0 inside the circle representing the majority decision element P10. Output lines of the majority decision element P10 are indicated by the lines projecting from the right side thereof. The two zeros (G0) in the circle representing majority element P10a designate a double value binary 0 constant control input and the three ones (lll) inside the majority element P10b designate a constant control input having a triple value of binary 1. It will also be noted that many of the majority decision elements have control input lines having a crossbar, for example, as shown on the control input [z2 for the majority element P10. The cross-bar indicates the windings are wound in the opposite direction to reverse `the phase of the binary signal applied thereto, e.g., a binary input signal of pi radians, corresponding to a binary 1 signal, is inverted to produce a binary signal control input having a phase of zero radian corresponding to a binary 0 signal. The purpose and result is to convert a binary l input signal to a binary 0 control signal.

DETAILED DESCRIPTION OF THE PARTIAL ADDER CIRCUITS (FIGS. 6, 7, 8 AND 9) Referring brieily to previously described FIG. 3, decimal unit #1 is shown to include partial adder [circuits 30, 32, 34 and 36. These partial adder circuits are responsive to two sets of four binary-coded decimal digit signals for the least signicant digits 7 and 5 of the augend 367 and addend 435, as shown. These signals are applied to the adder inputs and are distributed to the partial adder circuits 30, 32, 34 an 36 as shown in FIG. 3, to be operated on by these partial adder circuits to produce a partial sum (mod l0) of the digits 7 and 5 at the outputs Spia, SpZtz, Sp4a and S11-8a. Referring to FIG. 6, the details of the partial adder circuit 30 are shown to include majority elements P01, P02, P01a and P01b connected in a network to provided a binary 0 signal at the partial sum output Spla in response to exemplary binary l signals applied to inputs a1 and d1. The binary stages of each of the majority elements P01, P02, P01a, and P01!) in response to binary 1 signals at` the inputs a1 and d1 are shown in FIG. 6 by the binary digits (0) or (l) adjacent to the respective majority element. In FIG. 4b, Table 3 indicates the binary states of the CTI majority elements P01, P02, P0101 and P01!) in response to all the different possible combinations of binary 1 and 0 signals applied to inputs al and d1. In Table 3, under the respective column headings designating their respective majority elements, the zeros (0) have been omitted for clarity. It is to be understood that the binary l digits in any column position in this Table 3 designate that the corresponding majority element is placed in a binary l state and the absence of a binary digit at any column position designates thatthe corresponding majority element is placed in a binary 0 state. In View of the prior explanation of the operation of individual majority elements and networks of majority elements, the details of operation of the partial adder circuit 30 (FIG. 6) in response to combinations of binary signals O and 1 applied to inputs a1 and d1 should be clear, particularly in view of the following detailed discussion of its operation in connection with t-he exemplary binary signals l and 0 `applied to its inputs all and d1 and the later general discussion of its operation. The partial adder circuit 30, having only two inputs a1 and d1, will be discussed first to show the manner in which the lbinarycoder decimal digit partial sum (mod 10) output Spia is obtained directly to provide the least significant bit of the partial sum Sp1 of adder stage #1. As shown in FIG. 6, the partial adder circuit 30 comprises an exclusive OR logical operator including majority decision elements P01 and P02 which are operative during subclock I of operating cycle No. 1 (FIG. 2b) and majority decision elements Pillai and P0117 which are operative during subclocks II and III, respectively, of operating cycle No. 1. The control inputs r11 and d1 to the partial adder circuit- 30 are applied to both majority decision elements P01 and P02, as shown. When exemplary binary l signals are applied to bot-h al and d1 inputs, as illustrated, .a majority of binary 1 signals is present at the input of both majority elements P01 and P02. Accordingly, bot'h elements are placed in a binary l stateto provide binary l signals on their respective outputs.

The binary l signals on the respective outputs of majority elements P01 and P02 are coupled to control inputs of majority element P01a. One of these control inputs for the majority elementI P01a is inverted, as indicated in FIG. 6 by the cross-bar, to provide a binary 0 signal at this control input instead of a binary l sign-al. Since the majority element P0111 has a constant binary 0 input (indicated by the 0 in the circle) the majority of the signals (2 of 3) or the net signal is binary 0. Accordingly, the majority element P0101 is placed in binary 0 state and a binary 0 signal is produced at its output. Majority element P0119, operating during subclock III, has only a single control input which is coupled to the output of majority element P01a. Accordingly, the majority of binary signals (1 of l) at the input of m-ajority element P01b is binary 0 which places the majority element P01b in the binary 0 state to provide a binary 0 signal at the output Spla of the partial adder circuit 30.

In vie-w of the above explanation, an examination of circuit 30 will clearly show that if both the binary signals at the inputs a1 and d1 are O bits, a binary O signal -will likewise be produced at the output Spla. Furthermore, if the binary signal at one of the inputs a1 or d1 is a 0 bit and the other is a 1 bit, a binary l signal will be produced at the output Spla.

To summarize, the partial adder circuit 30 as shown in FIG. 6 is a network providing an exclusive OR function. This network is responsive to binary signals at inputs a1 and d1 to produce a binary 0 signals at the output Spla when both of the binary signals at the inputs a1 and d1 are 0 bits or 1 bits; and to produce a -binary l signal at the output Spla when a binary l signal is applied to only one of the inputs a1 and d1.

In the foregoing description of the operation of the partial adder circuit 30, t-he output of majority element 

12. A PARALLEL ADDER FOR SUMMING A PAIR OF PLURAL-DIGIT NUMBERS HAVING A RADIX N (WHEREIN N IS EQUAL TO EITHER 10 OR 2) COMPRISING: A PLURALITY OF ADDER STAGES EACH OF WHICH CORRESPONDS TO A RESPECTIVE DENOMINATION OF THE DIGITS OF SAID NUMBERS, EACH OF SAID ADDER STAGES COMPRISING A PARTIAL ADDER CIRCUIT FOR PRODUCING AN OUTPUT REPRESENTING THE PARTIAL SUM (MOD N) OF THE CORRESPONDING DIGITS OF SAID NUMBERS AND CARRY DETECTION CIRCUIT MEANS FOR PRODUCING CARRY INFORMATION SIGNALS INCLUDING BOTH AN ABSOLUTE CARRY SIGNAL AND A REDUNDANT, CONDITIONAL CARRY SIGNAL WHEN THE PARTIAL SUM IS AT LEAST EQUAL TO N AND FOR PRODUCING A CONDITIONAL CARRY SIGNAL ONLY WHEN THE PARTIAL SUM IS AT LEAST EQUAL TO (N-1); CARRY PROPAGATION CIRCUIT MEANS COUPLED TO SAID CARRY DETECTION CIRCUIT MEANS TO BE RESPONSIVE TO SAID CARRY INFORMATION SIGNALS PRODUCED FOR THE RESPECTIVE STAGE AND CARRY INFORMATION SIGNALS PRODUCED FOR ANY LOWER ORDER STAGES FOR PRODUCING FINAL CARRY INFORMATION; AND CARRY INCORPORATION MEANS RESPONSIVE TO THE OUTPUT OF THE RESPECTIVE PARTIAL ADDER CIRCUIT AND THE FINAL CARRY INFORMATION PRODUCED FOR ANY NEXT LOWER ORDER STAGE FOR PRODUCING AN OUTPUT REPRESENTING THE RESPECTIVE DIGIT OF THE FINAL SUM. 